Conventionally, there have been proposed a variety of connector devices each installed in an engine (see US 2010/0003841 A1). A conventional example of such a connector device is illustrated in FIG. 18. As illustrated in FIG. 18, a conventional connector device 50 is installed in a cylinder head 70 of an engine to pick up an output of a built-in fuel pressure sensor element (not illustrated). The conventional connector device 50 includes a wire harness side connector 51 and a sensor side connector 60.
The wire harness side connector 51 includes a housing part 52. A first terminal 53 is disposed in an interior portion on one end side of the housing part 52. An external terminal 54 is disposed in an interior portion on the other end side of the housing part 52. The first terminal 53 is connected to the external terminal 54 through wires W accommodated in the housing part 52. The housing part 52 includes a connector fitting part 52a housing the external terminal 54. An external connector (not illustrated) is fitted to the connector fitting part 52a. 
The sensor side connector 60 includes a sensor body part 61 in which a sensor element (not illustrated) is disposed, and a housing part 63 which is fixed to the sensor body part 61 and in which a second terminal 62 is disposed. A threaded part 61a is formed on the outer circumference of the sensor body part 61. By screwing the sensor body part 61 into a threaded hole 70a of the cylinder head 70, the sensor side connector 60 is installed in the cylinder head 70.
With the above mentioned constitution, the sensor side connector 60 is installed in the cylinder head 70 and thereafter, a head cover 71 is mounted on the cylinder head 70. Then, the wire harness side connector 51 is inserted into a hole 71a of the head cover 71 and fitted to the sensor side connector 60.
The sensor side connector 60 is screw fastened to the threaded hole 70a of the cylinder head 70. Accordingly, the rotational position (orientation) of the housing part 63 of the sensor side connector 60 is non-constant and furthermore, when fitting the wire harness side connector 51, the housing part 63 of the sensor side connector 60 is located deep in the hole 71a of the head cover 71. Therefore, the housing part 63 of the sensor side connector 60 cannot be visually recognized clearly, so that it is difficult to align the housing part 52 of the wire harness side connector 51 with a formal fitting rotational position with respect to the housing part 63 of the sensor side connector 60, causing a problem of inferior fitting workability.
In such a situation, this applicant has proposed a connector device having good fitting workability. This connector device includes a first connector including a first housing part in which a first terminal is disposed, and a second connector including a second housing part in which a second terminal is disposed. In operation, the first housing part and the second housing part are fitted to each other, and the first terminal and the second terminal are connected together at a fitting completion position. Then, the first connector includes a third connector rotatably attached to the first housing part, while the third connector includes a third housing part in which a third terminal is disposed. In the connector device, the first terminal and the third terminal are connected to each other through a wire. The first housing parts is provided with a guide rib part, while the third housing parts is provided with a rotational direction guiding part which guides the guide rib part in a manner that the first housing part and the second housing part are brought into their formal fitting rotational positions by the time when the first terminal and the second terminal start to come into contact with each other.
With the above mentioned constitution, even if the rotational position of the second housing part cannot be specified, the fitting operation between the first housing part and the second housing part could be accomplished with ease. Additionally, as the first terminal and the third terminal are connected to each other through the wire, it is possible to realize the improvement of reliability with respect to electrical connection, reduction in number of components, etc. in comparison with electrical connection using contacts, such as rotational contacts.